Association between neuropeptide oxytocin and male infertility

To investigate the relationship between oxytocin (OT) and male infertility, serum OT baseline concentration and oxytocin receptor (OTR) gene expression in fertile and infertile men were investigated.

Twenty obstructive azoospermia patients, twenty five idiopathic asthenozoospermia patients, twenty idiopathic oligozoospermia patients and twenty healthy subjects were taken into consideration. Serum OT baseline concentration was determined by radioimmunoassay. Moreover, serum concentration of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone (T) were determined by chemoluminescence to evaluate the correlation with OT. OTR gene promotor and OTR mRNA expressions were determined by polymerase chain reaction and reverse transcriptase-polymerase chain reaction, respectively. OTR protein expression was also performed by Western Blot.

Serum OT baseline concentrations in infertile groups were significantly higher than in fertile group (F0.05/2(2,82) = 8.29, p < 0.001). Serum baseline concentration of OT was not correlated with that of LH, FSH and T. There was no significant difference in gene sequences of OTR gene promotor and OTR mRNA when comparing infertile patients with fertile. Human OTR was in the form of oligomers and monomers, and the oligomers were in the majority containing tetramers and hexamers. Monomer expression was significantly higher in idiopathic asthenozoospermia and idiopathic oligozoospermia than that in obstructive azoospermia and control group (F0.05/2(2,82) = 115.50, p < 0.001). There was no significant difference in oligomer expression between different groups, but 20% of idiopathic asthenozoospermia cases showed a decrease.

Significantly different OT baseline concentrations and OTR expressions between fertile and infertile men strongly suggest that OT/OTR system is likely to be linked with male infertility, providing new insights into the pathogenesis and treatment of male infertility.